1. Field of the Invention
The present invention relates to a color image processing apparatus for use in a full color copying system, and more particularly to such a color image processing apparatus which includes a means for preventing the quality of a marker-enclosed image from being degraded by density irregularities of a marker that has been written on an original to be copied.
2. Description of the Prior Art
There has been known a color image processing apparatus for optically reading a color image, such as an image containing letters, a photographic image, or the like, as red (R), green (G), and blue (B) signals, converting these signals into recording colors comprising yellow (Y), magenta (M), cyan (C), and black (K), and recording a reproduced color image on a recording sheet based on the recording colors using an output hardcopy device such as an electrophotographic color copying machine.
One type of such color image processing apparatus has a marker color conversion circuit for converting the color of a black character or characters which are enclosed by a marker or markers on an original into the color or colors of the marker or markers.
As shown in FIG. 1 of the accompanying drawings, the marker color conversion circuit reads the area enclosed by the marker MC and the color of the marker, and determines the area and the marker color with respect to each scanning line. The marker color is determined at sampling points, each indicated by a dot ".", on the scanning lines.
Some marker color conversion circuits are designed to determine the recording density of an image enclosed by a marker MC depending on the density of the marker MC. If, however, the density of the marker MC has irregularities, those density irregularities appear directly as irregularities of the recording density of the image, resulting in a poor recording image quality.
When an image area is enclosed by an upper red marker MC(R) and a lower blue marker MC(B) as shown in FIG. 2, the image in the marked area which is recorded contains an upper image segment which is red and a lower image segment which is blue, so far as determination of marker color in terms of mere line unit is concerned. It would be better, from the standpoint of clear visual perception, if the image in its entirety were recorded in the same color as the first marker MC used.